/**
 * Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
 * For example,
 * Given [100, 4, 200, 1, 3, 2],
 * The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length: 4.
 * Your algorithm should run in O(n) complexity.
 */
/**
 * @author Ivan
 *
 */
package problem128_Longest_Consecutive_Sequence;